Scanning white light interference microscopy

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Micro to millimetre range structures can be measured at VTT MIKES using scanning white light interference microscope (SWLI). The SWLI (Bruker ContourGT-K) has sub-nm vertical and μm level horizontal resolution. It can measure square mm areas in a single scan.
The main features of the device are listed in the table below. Benefits of SWLI compared to other instruments with similar vertical resolution include large measurement area, ability to measure high steps and overlapping surfaces inside of transparent structures. Examples of objects suitable for measurement with SWLI: bearings, contact surfaces, topography and wear of surfaces, semiconductors and MEMS, medical instruments and implants, optical components, precision-machined components.

Real measurement uncertainty is case specific and it depends on the measurement environment, properties of the instrument and of the measured sample. At VTT MIKES we take care that the sample is clean, sample temperature is known, sample is well attached and properly aligned. Measurements results are traceable to the SI metre via our own transfer standards such as step height standards and laser interferometer.Measurements are done under consistent conditions and results are well documented.

Properties of the SWLI at VTT MIKES.

Property

Data

Optical x-y resolution

3.8 – 0.7 µm

Pixel size

7.2 – 0.2 µm

Vertical resolution

< 0.1 nm

Step height measurement: – repeatability – accuracy

< 0.1 %< 0.75 %

Sample reflectivity

0.05 % – 100 %

Maximum surface tilt smooth samples

3° (2.5× objective), 18.9° (20× objective)

Objectives

2.5× ja 20× objectives, 0.55×, 1× ja 2× zoom lenses

Measurement area:
– smallest magnification – largest magnification

(X × Y × Z mm3):3.5 × 4.6 × 3.50.4 × 0.6 × 3.5

Measurement area in pixels

640 × 480

Software

Vision64 Analysis Software, MountainsMap, MatLab

Maximum size of measured obejct

10 cm high × 20 cm wide, one dimension can be much longer

Ability to measure overlapping surfaces

2 surfaces in single measurementMaximum depth is dependent on refractive index, geometry and magnification, e.g. it is possible to measure through 0.3 mm thick glass7 mm maximum depth limited by working distance